1. Field of the Invention
The present invention relates to an evacuated blood collection tube for rapid blood coagulation, which is suitable for isolating serum of high purity from whole blood in a rapid and simple manner.
2. Description of the Related Art
The injection of heparin as an anticoagulant agent into biological organisms has been increasing in use in recent years, according to the development and diffusion of extracorporeal blood circulation treatment such as hemodialysis. Therefore, the possibility of sampling heparinized blood by means of evacuated blood collection tubes is increased in biochemical tests for the components of blood. Generally, in the biochemical tests, serum isolated from whole blood is used as a sample. However, heparinized blood has a disadvantage such as to be scarcely coagulated.
As a method for collecting serum rapidly, there has been proposed a method for adding protamine sulfate to whole blood so as to neutralize heparin (Japanese unexamined patent publication No. 58-1460). In case of biochemical tests performed prior to hemodialysis, the blood sample contains no heparin. Therefore, the blood sample is scarcely coagulated because the protamine sulfate itself in the blood collection tube has an anti-coagulation action. For this reason, it is necessary for operators to use a blood collection tube to which protamine sulfate has not been added when the blood sample is collected prior to hemodialysis. Accordingly, the procedures have been very complex because of the selection of tubes.
Then, there has been proposed a blood collection tube which contains 10 to 200 xcexcg of protamine sulfate and 0.1 NIH unit of thrombin as coagulation-promoting agents per 1 ml of collected blood (Japanese unexamined patent publication No. 62-253036). This blood collection tube has an advantage that blood coagulation is promoted owing to the presence of thrombin, irrespective of the presence of heparin. However, the blood collection tube is still unsatisfactory in sufficiently shortening the coagulation time because it takes about 15 minutes for blood coagulation.
The present invention has been developed to overcome the above-described disadvantages and an object of the present invention is to provide an evacuated blood collection tube for rapid blood coagulation, whereby serum of high purity can be isolated in a rapid and simple manner without fibrin deposition.
As a result of assiduous studies for solving the problems in the prior art, it was found that blood samples can be coagulated rapidly by employing a blood coagulation-promoting enzyme obtained by adding a small amount of thrombin into an appropriate amount of batroxobin.
Specifically, the present invention relates to an evacuated blood collection tube for rapid blood coagulation, which contains beads, each coated with a blood coagulation-promoting enzyme comprising thrombin and batroxobin. Preferably, the amount of thrombin per 1 ml of collected blood is 0.1 to 3 IU and the amount of batroxobin per 1 ml of collected blood is 0.5 to 2 BU. Additionally, the beads are preferably made of glass or polystyrene.
The evacuated blood collection tube of the present invention contains beads, each coated with a blood coagulation-promoting enzyme comprising thrombin and batroxobin. Thrombin is relatively economical and has less influence with respect to the amount thereof on the product cost. If the amount of thrombin is too great, however, deposition of fibrin readily occurs. If no thrombin is added, alternatively, blood coagulation time is not shortened. Preferably, thrombin is added in an amount of 0.1 to 3 IU per 1 ml of collected blood. Moreover, batroxobin is so costly that the amount thereof added has a serious influence on the product cost. If the amount is too small, however, fibrin deposition readily occurs, and coagulation time is long. The amount of baxtroxbin can range from 0.25 to 2 BU per 1 ml of collected blood and, preferably, 0.5 to 2 BU per 1 ml of collected blood. The blood collection tube preferably contains other blood coagulation-promoting enzymes such as an appropriate amount of thromboplastin.
The beads useful in the present invention are not particularly limited as long as the beads are compatible with the blood coagulation-promoting enzyme and do not adversely affect the blood coagulation reaction or coagulation time. Glass beads and synthetic resinous beads, such as polystyrene and polypropylene, are preferably selected as the beads on which the blood coagulation-promoting enzyme is to be coated. Generally, the beads have a spherical shape. Preferably, a particle size of the beads is 0.1 to 1 mm. A specific gravity of the synthetic resinous beads is equal to or larger than the specific gravity of blood cells so that the beads can transfer to a layer of blood clot during centrifugal separation.